Re: Crossflow V-4 conversion
Hello All!<br /><br />By heat exchanger, I'm am referring to the bolted plates on the rear of the block, in which water passes through, thereby "exchanging the heat" of the exhaust as it leaves the motor. On crossflow 140's, there is a bubble in the casting of this device. I believe Mr. Reeves calls this the "lower exhaust tuning megaphone". I can only assume that this causes less restriction for the exhaust, which probably increases the horsepower of the motor - especially at high speeds.<br /><br />My mistake on the oil-ratio. Instead of 16oz per 6 gallons, I mix 13.5 oz, which equates to approx. 56.9 to 1. This should help reduce my carbon problem, and judging from the looks of the crankshaft assembly, this is not having an adverse effect on lubrication requirements.<br /><br />I did notice some piston slap on the broken side a couple of trips before the breakdown. Come to think about it, the last block I had, which I rebuilt twice, broke a lower ring in the same location - at the exhaust port. In all 3 cases now, there is carbon buildup on the backside of the broken (lower) ring. This makes sense because this side is colder and would be more suseptible to caking. Incidently, I did not have a chance to rebuild my first block a third time. When I was washing the block during the 2nd rebuild, I inadvertently blew out one of the cross drill plugs for the oil passageway for the center crank bearing. Obviously, this is under vacuum. Apparently, the powerhead gasket was not installed correctly, and this thing was allowed to suck salt water from the bottom along with gas from the intake. Over a year, this lead to the demise of the crank, and ultimately the block. I won't do that again.<br /><br />After a discussion with the machinist, I decided to leave the 115 alone. An avid outboard racer, he tells me that in 140 configuration, the horsepower difference doesn't materialize until after 5000 rpm. For me, this doesn't help. I've got a fishing boat - put it on step and run about 4300 for long periods. I was looking for holeshot and its not going to happen. Given my prevous info, the boat is propped right and I'll just have to live with everything else. It's just not worth the extra effort and fuel consumption. BTW - the current block had OEM pistons in it. I asked the machinist about using forged pistons (Wiesco), but he suggested going with the cast ones instead. Says the extra weight on the crank is unnecessary. Also, I use the stock spark plugs - champions. Finally, after the first carbon failure, I tried the OMC oil. When it happened again, I went back to Itasca and this does'nt seem to matter. I am open to opinions on this though.<br /><br />Awesome discussion - thanks to all of you for your input! I will visit this webpage from time to time.
